Certain chemical compounds have long been known in the art to possess the desired quality of imparting softness to textile fabrics. The quality of "softness" or being "soft" is well defined in the art, and, as used herein, means that quality of the treated fabric whereby its handle or texture is smooth, pliable, and fluffy, and not rough or scratchy to the touch. Known generally as "fabric softeners," these compounds have long been used by homemakers in the laundry, and by the textile industry to soften a finished fabric.
Additionally, many of these compounds act as antistatic agents to reduce the "static cling" of the treated fabrics. Static cling is generally the phenomenon of a fabric adhering to another object or to parts of itself as a result of static electrical charges induced on the surface of the fabric. It can also cause the adherence of lint, dust, and other undesired substances to the fabric. It is noticeably present in unsoftened fabrics that are freshly washed and dried in an automatic hot air dryer. By softening and reducing the static cling of a fabric, it is more comfortable when worn. Such treated fabrics additionally are easier to iron, and have fewer hard-to-iron wrinkles.
Perhaps the most common fabric softeners and anti-static agents known in the art are cationic compounds, especially amines such as quaternary ammonium and imidazolinium salts. These compounds are widely marketed for home use in the form of liquid emulsions. They must be added to the laundry in the rinse cycle, not the wash cycle, because cationic fabric conditioners interact with anionic substances present in laundry detergents such as anionic surfactants and builder salts, thereby rendering both relatively ineffective. A commercial fabric conditioner of this type is Downy.RTM. (The Proctor & Gamble Company, Cincinnati, Ohio).
Another method of softening fabrics involves the utilization of impregnated nonwoven dry fabric softener sheets that are added to the dryer along with damp (wet) laundry. The ingredients are released largely in a nonuniform manner from the dry sheet into the laundry by the abrasive action of tumbling in contact with the laundry, moisture from the laundry and the heat of the dryer. In general, the composition coated on these sheets is composed of cationic softening agents, antistatic agents, dispersing ingredients to help provide a more uniform ingredient release and fragrance. A commercial dryer sheet of this type is Bounce@ (The Proctor & Gamble Company, Cincinnati, Ohio). The disadvantage with these dryer fabric softener sheets is their relative poor softening ability versus the liquid softeners that totally penetrate the laundry fabrics in the last rinse of the washing machine cycle.
It has previously been impossible to attain the benefits of a liquid fabric softener, i.e., greater softening ability and dispersibility, in the dryer using the dryer sheets. Moreover, using liquid fabric softeners in the washing machine last rinse cycle require all the articles in that laundry load to be softened. In some instances, the user may desire to control the softening of the clothing, in which case, the user must divide the laundry into those articles they desire to be softened and those they do not. This results in inconvenient expenditures of time in creating additional wash loads and drying time.
It is therefore an object of the invention to provide a method of softening fabric articles in the home automatic dryer with liquid fabric softener ingredients resulting in superior softening ability. It is a further object of the invention to provide a method of softening fabric articles without having to divide articles of clothing into multiple groups according to the softening and or treatment desired, thus incurring such inconveniences and disadvantages mentioned above. Additional objects of the present invention will become readily apparent to persons skilled in the art from the following discussion."